The structure of the active layer of a conventional AlGaInP light-emitting device is normally a double heterostructure (DH) or multi-quantum wells (MQWs), and a portion of the light emitted from the active layer towards the growth substrate is totally absorbed by GaAs substrate used in the AlGaInP light-emitting device. Therefore, the external quantum efficiency of this kind of conventional AlGaInP light-emitting device is low. Besides, the thermal conductivity of GaAs is only about 44 W/m−° C. which is too low to dissipate the heat generated by the device.